run-tests: fix some io ordering backported from default

merge with stable

test-revert: add case where file is tracked but deleted in working directory

test-revert: add case with untracked files with unique content This test highlights similar misbehavior as its parent changesets.

test-revert: add case with untracked files with reverted content This test highlights similar misbehaviors as its parent changesets.

test-revert: add case where file exists but is untracked in working directory This test highlights a small misbehavior in output when reverting to another revision not including the untracked file.

test-revert: add case where the file is marked as removed in the wc Unlike untracked, the file is also missing from the working directory. This test highlights a small misbehavior in output when reverting to another revision.

test-revert: add case where wc content is different from "base" and "parent" This test highlights a case where backups are not created and the user may lose data.

test-revert: add case where wc content is already reverted to base content This test highlights multiple misbehaviors of revert. We augment the test comments accordingly.

test-revert: add case where file exists neither in "base" nor in "parent"

test-revert: add case where the file is removed between "base" and "parent"

test-revert: add case where file is unchanged between "base" and "parent" This test highlights a minor misbehavior in the message displayed during an explicit revert with a target revision.

test-run-tests: fix stdout/stderr io ordering

test-revert: add case where file is added between "base" and "parent"

merge with stable

test-revert: add methodical revert to "base" with explicit file path We now also test reverting file to another revision's content. However this differs from previously introduced test by using the explicit path of each "case file" when calling revert. This should result in the same result regarding file content and backup creation, but the output of the `hg revert` call should differ.

test-revert: add methodical revert with explicit file path We now also test reverting file to the working directory parent content. However this differs from the previously introduced test by using the explicit path of each "case file" when calling revert. This should result in the same result regarding file content and backup creation, but the output of the `hg revert` call should differ.

test-revert: add methodical revert to "base" We now also test reverting s file to the content of another revision. This is still done using the `--all` flag.

test-revert: add methodical revert to parent for working directory Now that we can automatically generate states, we need to actually run revert on them and check the result. While running such tests we are checking multiple elements. The output of the `hg revert` command, the resulting content of file, and the creation of backup file. The first practical test is using the simple case `hg revert --all`, reverting all files to working directory parent content.

test-revert: display the list of all generated cases This will help to track all existing cases. (still very simple now)

test-revert: also create a text version of the snapshot The text version is just a list of existing files with their content. We use a small custom script for that. This is going to be very useful for comparing revert results with revert target content.

hg-test-mode: make exit code highlight work again

test-revert: prepare methodical testing of revert cases We introduce a script to generate revert cases and use it to prepare a test repo. See the inline documentation for details.

test-revert: drop useless comments There are multiple comments explaining the expected output of commands. This is an old relic of the pre-unified test era. We remove them for uselessness.